Caladenia arenaria Fitzg. Recovery Plan
Threatened Species Unit, Western
The State of New South Wales, Department of Environment and Conservation, 2004
15 Alternative management strategies
- 15.1 No action taken
- 15.2 No monitoring
- 15.3 The longer term issue of White Cypress Pine
- 15.4 Studies of the fungal symbiont and the pollinator
- 15.5 Re-introduction in potential habitat
Caladenia arenaria has:
- a total known population of approximately 2000 individuals
- four discreet populations, each covering a limited area
- several threatening processes
- an apparent loss of two populations in the last 10 years.
There is a high likelihood of extinction. No management action is an inappropriate response.
A cost effective option could be to fence all populations and undertake weeding, without the expense of the experiment or annual monitoring. The disadvantage of this approach is the threats recognised may not, in fact, have any measurable impact on C. arenaria. Pre-empting the outcome of the experiment could mean that any fencing and weed control works are a waste of resources, or worse that they have a deleterious impact. For example in the absence of some grazing the grass sward may competitively exclude C. arenaria. The precautionary approach where the effects of management are measured is preferable. Hence, annual monitoring is a necessary part of the recovery strategy, particularly given the variability in plant numbers in any one year due to climatic conditions or other variables.
The occurrence C. arenaria in dense stands of juvenile or reproductively mature but suppressed White Cypress Pine may require investigation in the long term. The small cypress pines will eventually self thin, albeit at a very slow rate. The habitat currently occupied by the orchid populations may then become unsuitable. Juvenile or suppressed pines may simply afford protection from other threatening processes, or it may be that stands of juvenile or suppressed pines are necessary for the other reasons, for example, they may have the highest densities of the orchids fungal symbiont.
If structurally suitable stands of pine are required, the mature pine stand around the juvenile or suppressed pine may have to be manipulated to promote recruitment of pine seedlings, providing habitat for the orchid population to expand or colonise. White Cypress Pine successfully recruits in open habitats only hence if recruitment of pine is not occurring naturally the dominant pines must be thinned to provide suitable conditions.
The necessity of undertaking this action can be assessed after the experiments into the impact of the threatening processes have shown results. It may be decades before white cypress stand structure is a major issue for C. arenaria. There are several possible experiments that could be conducted. Seed could be sown into suitable areas carrying pines or seedlings planted. Alternatively, the juvenile pines among the populations could be thinned. This option is inappropriate at present, given the small total area occupied by the orchid populations. If the species proves to be more widespread in Buckingbong or Yarranjerry State Forests this option could be considered.
Studies of the fungal partner and wasp pollinator could be undertaken. The fungal partner has been isolated from several species of Caladenia. The difficulty is that no fungus isolate has ever become fertile in vitro, and so cannot be identified. Hence, establishing the distribution of the fungus in the field is problematic. Another complication is that after some time isolates can become pathogenic to orchid seed (Kingsley Dixon pers. comm.). Solutions to these challenges are likely to take a substantial commitment of resources and time, beyond the scope of this plan.
Investigation of the pollinator would assist understanding of hybridisation, and help define habitat elements critical for the pollinator. This has not been included in the plan, since it appears that there is an adequate level of pollination in all populations. The implicit assumption is that the habitat presently occupied by the orchids provides for the requirements of the wasps. Further studies would be informative, but are not required for recovery at this stage.
Once there is some understanding of the population dynamics and germination biology re-introduction could be considered in potential habitat. This measure should be considered when the review of the plan conducted.